Document Viewer

I have Document Viewer which I use to read books in pdf . If i am at, say, page 100 in book one and close it then open book two at the start, when i go back to book one it is at the start. It seems going to page one brings all books to page one. Usually I can go between books and each one will open where i closed which is the way I want it.

This happened me before and I cannot recall how I fixed it. If anyone knows I would appreciate it